1. Field of the Invention
The instant invention relates to syringes for inflating a balloon in a balloon catheterization device and to the systems and methods associated with balloon catheterization (transluminal angioplasty procedures).
2. State of the Art
Numerous syringes for balloon catheterization are extant in the art. A representative sampling of such syringes are disclosed in the following patents: U.S. Pat. No. 5,047,015 to Foote et al.; U.S. Pat. No. 4,832,692 to Box et al.; U.S. Pat. No. 4,651,738 to Demer et al.; U.S. Pat. No. 4,940,459 to Noce et a).; U.S. Pat. No. 4,583,974 to Kokernak and U.S. Pat. No. 5,084,060 to Freund et al. An exhaustive list of additional patents exists in the references cited portion of the Foote et al patent.
Devices disclosed in the above-identified patents are quite similar in structure; having a barrel and plunger or piston configured so that the piston may be screwed into the barrel in small increments to increase pressure on fluid within the barrel. Ultimately, the pressurized fluid flow into the balloon in a slow, controlled manner to inflate the balloon. Generally, all syringes disclosed in the above-identified patents have a quick release mechanism whereby the threaded engagement between threaded piston rod and the internal threads within the syringe body are quickly disconnected, allowing the piston rod and piston to slide freely within the device and be quickly retracted to reduce rapidly fluid pressure within the balloon.
Various techniques and means are employed to bring about the disengagement between the threaded portions of the piston rod and the syringe housing. In the Foote et al. patent the threads on the piston rod are permitted to retract when a trigger mechanism is pulled to cause the piston rod threads to slide along an inclined plane to remove them from contract with the threads of the syringe body. In Box et al. a lever on top of the syringe is pushed towards the syringe by the palm of the hand to press against a threaded member to push that threaded member away from contact with the threads of the piston rod.
In both the Box et al. and Foote et al. devices a spring member is used to maintain the two threaded members in contact with one another. In the Kokernak device, a locking mechanism rotates and is locked in place by spring loaded balls which fit into detents. Thus, in all three patents, springs are relied upon to hold the threads in an engagement position.
Although these devices may work well, there is the risk that a spring will fatigue and allow the threads to disengage at an inopportune or critical moment. Furthermore, in the manufacture of the device some machined piece of metal or plastic might become lodged in the spring cavity thereby preventing the spring from being depressed, thereby restraining the piston from disengagement. Either of these situations could result in adverse consequences to a catheterization patient.